1. Technical Field
The present invention relates to a cache server control device which controls cache servers used in a content distribution system, a content distribution system, a method of distributing content, and a program.
2. Background Art
Recently, the speed of data communication network, such as the Internet, has been upgraded. It has also become possible to transmit video contents by high-vision broadcasting with high image quality, by virtue of adoption of H.264/AVC codec. IPTV services may, therefore, be expected to be brought into full operation.
VOD (Video On Demand) service is one of such IPTV service. A content distribution system for realizing the service is configured by a content storage which stores video contents, and a distribution server which distributes the video contents. On the other hand, the content distribution system is required to distribute video contents in a stable manner to a large number of subscribers. A variety of technologies for fulfilling the requirement have been developed.
For example, Japanese Laid-Open Patent Publication No. 2009-182629 discloses a technology of preliminarily allocating to distribution servers, contents which satisfy specific conditions. Japanese Laid-Open Patent Publication No. 2009-165118 discloses a technology of placing the contents in local caches of user terminals before viewing such contents. Japanese Laid-Open Patent Publication No. 2808-072484 discloses a technology of preliminarily predicting a time zone in which loads of the instruments which hold video contents will become heavier in a home area network system, and moving the video contents to other instruments before getting into the time zone.
Japanese Laid-Open Patent Publication No. 2009-033760 discloses a technology of preliminary placing head chunks of the contents in local caches. Japanese Laid-Open Patent Publication No. 2007-080161 discloses a technology of separately holding the full contents and the head portions of the contents, and allowing the clients to concurrently download the full contents and the head portions of the contents.
Japanese Laid-Open Patent Publication No. 2009-237918 discloses a technology of supervising loads of local servers which distribute the contents, and determining the number of contents to be copied to local servers depending on the loads, thereby preparing a copy schedule.